1. Field of the Invention
The present invention relates to a circuit breaker and, more specifically, to a shield apparatus for protecting elements that are internal to a circuit breaker.
2. Background Information
Circuit breakers, including molded case circuit breakers, have at least one pair of separable contacts. A first contact, known as a “stationary contact”, is fixed within the housing. The other contact, the “movable contact,” is disposed on a movable contact arm that is a part of a contact arm carrier assembly which is coupled to an operating mechanism. Both contacts are disposed on conductive elements that are in electrical communication with either the line or load coupled to the circuit breaker. The operating mechanism is structured to move the movable contact between a first, closed position wherein the fixed and movable contacts are in contact and are electrically connected, and a second, open position wherein the movable contact is spaced from the fixed contact whereby the contacts are electrically disconnected. The operating mechanism may be operated manually or by the circuit breaker's trip mechanism. When a circuit breaker has multiple poles, each pole has its own set of separable contacts.
Each set of contacts is typically disposed within a separate contact chamber. The housing typically has a base portion, in which the majority of components are disposed, and a primary cover. The arc chamber is structured to dissipate an arc following separation of the contacts. That is, when the contacts are separated an arc may form, especially during an over-current event. The arc is dissipated in the arc chamber but the arc still creates gases and possibly a spray of molten debris. A problem typically exists due to the possibility of the blowback of arc gases and molten debris into the contact arm carrier assembly or the operating mechanism or both. The arc gases are typically vented through an exhaust. However, the molten debris and the arc gases, which may be corrosive, can impact on the contact arm carrier assembly components or the operating mechanism components or both, causing damage thereto. There is, therefore, a need to protect certain components that are internal to a circuit breaker during an arc event.